Hello gurus, I have a mental experiment that I'm wrangling with. Assume for a moment that two craft (Ship A and Ship B) are approaching each other at a significant fraction of c. Let us also assume that I, the observer, am in a stationary craft a large distance away rotating with the plane given by the vector of the two approaching craft, keeping one of them (Ship A) stationary in the center of my field of vision. I have two questions: 1. Since I have no way of measuring the velocity of Ship A in my frame, is it assumed to be zero? 2. What would I measure as the velocity of Ship B? I'm no mathematician of this level, but by all means don't dumb it down for me, as I'm really trying to pick some of this up.